Circulation timescales of Atlantic Water in the Arctic Ocean determined from anthropogenic radionuclides
<p>The inflow of Atlantic Water to the Arctic Ocean is a crucial determinant for the future trajectory of this ocean basin with regard to warming, loss of sea ice, and ocean acidification. Yet many details of the fate and circulation of these waters within the Arctic remain unclear. Here, we u...
Main Authors: | , , , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2021-01-01
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Series: | Ocean Science |
Online Access: | https://os.copernicus.org/articles/17/111/2021/os-17-111-2021.pdf |
Summary: | <p>The inflow of Atlantic Water to the Arctic Ocean is a crucial determinant for the future trajectory of this ocean basin with regard to warming, loss
of sea ice, and ocean acidification. Yet many details of the fate and circulation of these waters within the Arctic remain unclear. Here, we use the
two long-lived anthropogenic radionuclides <span class="inline-formula"><sup>129</sup>I</span> and <span class="inline-formula"><sup>236</sup>U</span> together with two age models to constrain the pathways and circulation
times of Atlantic Water in the surface (10–35 <span class="inline-formula">m</span> depth) and in the mid-depth Atlantic layer (250–800 <span class="inline-formula">m</span> depth). We thereby benefit
from the unique time-dependent tagging of Atlantic Water by these two isotopes. In the surface layer, a binary mixing model yields tracer ages of
Atlantic Water between 9–16 years in the Amundsen Basin, 12–17 years in the Fram Strait (East Greenland Current), and up to 20 years in the Canada
Basin, reflecting the pathways of Atlantic Water through the Arctic and their exiting through the Fram Strait. In the mid-depth Atlantic layer
(250–800 <span class="inline-formula">m</span>), the transit time distribution (TTD) model yields mean ages in the central Arctic ranging between 15 and 55 years, while the
mode ages representing the most probable ages of the TTD range between 3 and 30 years. The estimated mean ages are overall in good agreement with
previous studies using artificial radionuclides or ventilation tracers. Although we find the overall flow to be dominated by advection, the shift in
the mode age towards a younger age compared to the mean age also reflects the presence of a substantial amount of lateral mixing. For applications
interested in how fast signals are transported into the Arctic's interior, the mode age appears to be a suitable measure. The short mode ages
obtained in this study suggest that changes in the properties of Atlantic Water will quickly spread through the Arctic Ocean and can lead to
relatively rapid changes throughout the upper water column in future years.</p> |
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ISSN: | 1812-0784 1812-0792 |